Midterm 2 - Lecture 8 Flashcards
Direct vs Indirect impact of infectious diseases on production
Direct: drop in milk production (mammary gland)
Indirect: ill health on young animals or an insult to an organ or body structure distant from the mammary gland
Mastitis
- inflammation of the mammary gland
- infection of the mammary gland is the most common cause of mastitis in dairy cattle and only cause of production disease
Subclinical mastitis
- will diminish milk returns like clinical but to a lesser extent
- marked reduction in the overall milk yield to the producer if many cows are affected
Does clinical or subclinical mastitis pose a greater impact on profit?
- subclinical; for every case of clinical mastitis in the herd, there are btw 15 and 40 subclinical cases
- ~80% economic loss
Routes of mastitis infection
- hematogenous
- percutaneous = skin wound
- teat canal = main route
What is pathogenesis of mastitis dependent on?
- agent (pathogen)
- microbial ecology (environment)
- host health
What does transmission of mastitis depend on?
- amount of infectious agent in her enviro
- efficiency of milking personnel, machine and milking parlor hygiene
What is susceptibility of a cow to mastitis related to?
- The Epidemiological triad/ triange
- Agent-Host-Environment
Agent-Host-Environment
Epidemiological Triad/Triangle
3 phases of mastitis development
- invasive phase
- infection phase
- inflammation phase
Invasive phase of mastitis
- bacteria in barn or enviro
- amount of contamination on the apices of teat
- injury to teat sphincter and tone of teat spincter
- presence of antibacterial substances in teat canal
Infection phase of mastitis
- type of bacteria and its ability to adhere to mammary epithelium and multiply in milk
- susceptibility to commonly used antibiotics
- previous injury to teat, or concurrent infection
- stage lactation: first 2 months, most susceptible
- infections also occur during dry periods
When are cows most susceptible to mastitis infection?
- first 2 months of stage lactation
Inflammation phase of mastitis
- pathogenicity of bacteria matters
- reactivity of tissue; previous or concurrent infections = more tissue rxn
Subclinical mastitis vs Clinical mastitis (types of mastitis)
- Subclinical: no obvious indication of infection
- Clinical:
- Peracute: minimal clinical signs and can be deadly
- Acute: swelling of udder and purulent discharge in milk
- Chronic: long-term drop in milk production, udder may be hard
For every case of clinical mastitis in a her, how many subclinical cases are there?
- btw 15 and 40
Contagious mastitis
- the primary habitat of the organism is the udder (poor survival in enviro)
- most often cause sub-clinical and chronic infections
- transmission = contaminated fomites
Staphylococcus aureus
- major cause of mastitis
- can cause heavy loss of production and peracute/acute death
- chronic from is most economically important
Environmental mastitis
- bacteria survives in environment (oil, feces, bedding, water etc)
- occurs environmental contact: during or btw milking’s
- really any organism found in the enviro could cause environmental mastitis
Mastitis treatment
- clean equipment and enviro
- ‘strip the milk’ = milk affected udder every 3 hrs for the first 24-72 hrs
- intramammary infusion of antibiotics
- dry period is best for incidence of chronic mastitis
Pododermatitis (foot rot)
- a contagious disease that can cause both severe acute and chronic lameness in cattle
What organisms cause foot rot?
- Fusobacterium necrophorum causes initial infection followed by bacteroides nodosus
What is pododermatitis characterized by?
- moist dermatitis that is around coronary band and interdigital space
- infection often tracks into joints of the hoof causing chronic arthritis, tendonitis, desmitis and lameness
- cattle become inappetent and drop wt and milk production
How is pododermatitis spread?
- via contact with contaminated cattle or the enviro; once microbe is seeded in enviro its hard to remove
- transmission occurs around high-traffic areas (feed trough, gates, barn exits)
When does pododermatitis most often occur?
- when there is a lot of moisture aka standing in mud or manure for long time
- when cattle are exposed to hard surfaces for long time or stony ground/sharp gravel
Pododermatitis treatment
- clean up the environment and remove source of infection
- systemic antibiotics
- surgical removal of infected tissue
- foot bath of 5% copper sulfate or 5% formalin
- zinc supplement to diet
- vaccin for F. necrophorum
Economic impact of foot rot on Beef
- 75% of all lameness diagnosed
- wt loss: ~0.5 lbs/day
- loss in wt gain, treatment costs, decreased breeding efficiency, culling animals
- PREVENTION MORE EFFECTIVE THAN TREATMENT
Is prevention more effective than treatment for pododermatitis?
YES
